This invention relates to electrostatic air cleaners and has application to both single and multi-stage air cleaners.
Electrostatic air cleaners are used to remove particulate matter such as smoke, oil mist, and pollen from the air circulated in dwellings, factories, and other structures. Generally, they may be characterized as a group of spaced electrically charged plates between which a stream of air is directed. Alternate plates of the group are electrically charged oppositely so as to establish a potential difference between adjacent plates. Particulate matter carried into the plate group by an airstream is electrically charged by its passage in proximity to a charged plate of the stack and is then attracted and adheres to one of the oppositely charged plates and is thus removed from the air which is then recirculated in the structure. The construction so far described is generally referred to as a single stage precipitator.
To more effectively accomplish charging of the particulates, some single stage devices have one set of plates positioned further upstream of the air flow than is the oppositely charged set. Thus, the particulate matter enters first a region of electrostatic potential between the like charged plates and is charged before entering a region between the oppositely charged plates to there be removed from the airstream.
Multi-stage precipitators carry the concept just described a step further by having a grid of wires or plates, referred to as an ionizer grid, upstream of the collector plates. The ionizer grid may be charged to an electrical potential different from, and preferably higher than, that of the collector plates to more effectively charge the particulates. Precipitators with one plate group and one ionizer grid are referred to as being of two-stage type. Other multi-stage precipitators are constructed using various combinations of ionizer grids and plate groups through which an airstream passes in succession.
Because collected and adhered debris greatly reduces a precipitator's efficiency and effectiveness, it must be removed periodically. The cleaning of electrostatic air cleaners has been a problem because of the close spacing of the plates and the high voltages applied to the closely spaced, oppositely charged plates. Care must be exercised to see that the plates are cleaned effectively and are not electrically shorted together or to a ground. For this reason, some devices require periodic shutdown and disassembly so that the plate groups can be removed for washing. Other devices are rappers or shakers which strike or vibrate the plates to loosen collected debris and cause it to fall from the plates to the bottom of a housing where it collects for periodic removal. Other devices use an intermittently applied water film which flows over the collector plates while electrically uncharged to wash away collected debris. All of these cleaning methods suffer from disadvantages. Some do not do a good job of cleaning, others are complex and expensive, others are inconvenient and reduce the air cleaner's effective working time and increase maintenance requirements.
In one form of the air cleaner of this invention, each of two separate base members mounts a set of multiple spaced collector plates which project generally perpendicularly therefrom. The collector plates are preferably of similar length and shape. The base members are spaced apart with the plates of each projecting toward the other base and are shiftable between a use position and a cleaning position. In the use position the plates are interposed and equispaced. In the cleaning position the base members are further spaced apart and the plates are at least partly withdrawn from interposed relationship. The spacing of the bases in their use position is chosen to provide a space to receive a pair of slotted scraper plates, each mounted adjacent to a base and adapted to scrape the plates of the adjacent base when the base members are shifted relative to the scraper plates.
In two or multi-stage precipitators, a scraper may scrape the wires, or the plates, or other elements of the ionizer grid.
Another embodiment of the invention includes two spaced parallel shafts, each of which carries multiple radially projecting spaced circular discs. The shafts are journaled and so spaced and positioned that the discs of each shaft are interposed between those of the other shaft and spaced from adjacent discs and from the opposite shaft. An electrical charge is applied to the discs so as to establish an opposite charge on adjacent discs. An airstream from a structure is directed between the interposed discs. The discs rotate and pass through scrapers which remove accumulated debris. As previously described, an ionizer grid may be positioned in the airstream in advance of the discs to effectively charge the particulates.
It is an object of this invention to provide a uniquely constructed air cleaner with means for scraping clean the collector plates of the device.
Another object is to provide an air cleaner wherein the ionizer grid is provided with scrapers for cleaning thereof.
Another object is to provide an air cleaner which is efficient and economical.
Another object is to provide an air cleaner which may be quickly cleaned.
Other objects will be apparent from the following specification.